Telephone system



Nov. 6, 1928. 1,690,241

v H. w. O'NEILL TELEPHONE SYSTEM Filed Margh 31. 1926 Patented Nov. 6,

- -F lo-E 3mm? w. ou'm'pn, or EEHHURSII; YORK, JALSSIQNOB mo WESTERN ELECTRIC 00M- N; Y; A conronnrlon or NEW YORK;

' mnnnpnoun szs'rnm.

Annl pti filed ar h 31, 192e, Serial m asses telephone set ordinarily due to the; receiver and conversely ito'sprevent Loss in the energy incoming to the receiver ordinarily due to th ansm tter.

Another object is tocontrol output of sidetone in the'receiver of a telephonetset.

The invention has been embodied in an ordinary su scnib pr t lerhenesetfie m ing the usual induction coil and a transmitter and receiver element respectively includ ed in the utputnand input circuits. voice current responsive deyice' s included 1n the output circuit with the transmitter so as to become actuated YVllBIl t hQz t ansmitter is used, while a second deuce 11s arrangedto be controlled by the yoice current responsigve devi o p a t y o h lly remove hewmv lfrointhe input-circuit depending on whether 01- not a side-ton {eff t is des ed Qn t other hand, While the recei qer is; normally connected across the input-circuit,;thei-nduction coil isunot :sotconnected but is arm-ag to be included in placeof the receiver when the transmitter is actuated. Hence, the -actuation of ithe transmitter may remoye the receiver and connect the transmitter through the inductioncoil tQgthQ output circuit,

'lellephone instruments or sets, iwhether employed at subscriber stations-neat tele-v conduotors.

phone switchhoards, are, in; generalgconnected by twoconductors which serve tor both outgoing transmission [and tor incomingtransmission of, a: telephone conyersati'on. This use of buttwo conductorsusually-ohjtains irrespeotiwe ofiwhether zit-telephone set may he connectedkfor service over circnits where the main 91m sectiommay be formed of two conductors; or-1nay-be ion-med qt four ncct both the transmitterjandifithe receiver-{of i a line, while under'incominghmm iSS 011, a

ortion ot the energy is absorbed. in rtheieircuits ofi the tr anisrnitter therefore may not be available foruse in the telephone re-' ceiver. i p 1 c c i In the use of telephone sets, an effect co n- -mon'lyl referred to as side-tone is: produced.

This is principally due to the fixed inter connective relation oft-he transmitter and receiv eras when the transmitter may beQin use axportipn of the speech jeIl elfgy is taken up by the receiver ,With the} result thatisicletone produced. A f ur ther source of side tone is. from extraneousor roomv noises which may b p ke p by a ansm tt an t derecl effectivein the associated receiver of side-tone adyersely affects telephone trans-v mission inthree major ways. Firsti allsidenis sion. Secondflf a person speaks loudly, the resulting greater yolurne of sideetonemomentarily reduces-the sensitiveness of,- the 'speakers hearing thereby rendering it more difficult to understand incoming transmison, an -thi be ause of. he-" npl an feet 0t anexcessof side tonea speaker is in-.

clined to l-owe! the voice, thus reducing the amount of outgoing transmission. 'On the o her ha d, b efi a L i -ton may be described as a limited(yr-predetermined amount of sound, produced from outgoing speech only. Such side-tone may serve as a guide let fleto th 'o um nd-th amod tion he vo ce-and %a1s may s rve to ndice whetherone may lbespeakingimproper proximity-to the transmitter of; z -telephone set.

In telephone sets of the types. where the igeceiveris connected in series with the output circuit oi the associated transmitter, a maximum volume of side-tone will invariably he pi -resent. The greater pontion of such sidetone is Cletrimentaljto transmission and 1n at telephone; switchboands. The latter sets I e sua ly ased: On a? tw k m -re ne which is fo me 1 1 u pu :e -r it ta transmitter with jthe circuitsl of a receiver; insnch a manner that whenthe exteinor loads tone-from room or extraneous noises tendsfto decrease the lntelligibllityoi incomingtransloo 'etiective throu h the coil and balancing of the set may he connected to a line the impedance of which is equal to the impedance l()()lil1l f .into the network, a minimum volume of side-tone only may be set up in the receiver. Although arrangements oithe latter sort may, to a certain extent improve the condi tions as to excessive or detrimental side-tone, the idle transmission losses for both outgoing and incoming spc ch, as above pointed out, are usually in excess of the losses had with the simple series arrangement already mentioned.

A further cli'ect detrimental to telephone transmission is due to a iihenomenon encountered in so-called L l-wire working, which is commonly l'el'errcd to in the art as echo ctl'ect. In t-wire systems, a line section prop or is formed of two pairs of conductors. one pair for carrying tiransn'iission in one direction, as from east to west. while the other pair serves for transmission in the opposite direction. as from west to east. At each tier minus, coil systems and balancing networks are usually provided so that a l -wirc line section may merge into Q-Wire circuits l'or serv ice to respective telephone stations or sets. in circuits for commercial service, an appreciable amount of speech energy may become g vstems so that voice currents arriving over a pair from an eastern point may flow into and return to the originating point over the op posite or west to east transn'iission pair. A similar but inverse eti'ect is present under transmission in the opposite direction, from west to east. In case the length of a -t-wire line may be limited so that an inappreciable time is required for a circulating voice current to traverse the line section in returning to the originating station, the returning cnergy may merely tend to augment the sidctone in the receiver at the latter point. in practice, however, the length of t-wire circuits usually such that an appreciable time intervenes hetwecn the instant of generation of a voice current and its return and manifestation in the receiver of the originating instrument. This e'tieet in the ear of a person speaking is that of an echo, and for this reason this phenomenon is commonly relerrcd to as an echo etlect. ()u long circuits this is olriectionahle to the point of totally disabling a conversation. As a remedy for such etl'ects systems have heen provided for use with a;- wire ci1'cuit s.'and are commonly referred to as ec-ho-suppressor systems.

In addition to the operations of: transmission and reception oi speech. telephone sets when employed at telephone switchlmards are usually arranged for the carrying out of so-called click busy test operations.

Que feature of this invention is the provision of a telephone set in which the receiver may not cause loss in the output circuits of its associated transmitter, while, conversely, the

output circuits of a transmitter may not ahsorh or cause loss of incmning speech energy intended for the receiver.

Another feature is the provision of means whereby when desired, a limited and suitable amount only ot encrgv from a. transmitter may he rendered cliective with the associated receiver oi a telephone set to provide hencl'icial sidetone, while etl'ccts arising from large volumes of voice energy or from extraneous or room noises which would rcsult in (.let-rimental side-tone may he substantially incapable of producing a detrimental amount of side-tone in the receiver 01'' a set.

Another feature is the provision of a tele' phone set system for eliminating side-tone or echo etl'ects peculiar to :l-wire line cir uits and to permit so-called ccho'supprcssor arrangements, in general, to he dispensed with in connection with circuits of the last. men tioned type.

ltnother feature of the invention is the provision of a telephone set which in addition to a tint-ding the advantages set forth in thc tforcgoiug older-ts. may also be employed in performing busy test operations.

.ln carrying out the present invention. a switching svstem capable of control by energy from voice currents is coordinated with the circuits of a. telephone set in such a manner that for incoming transmission, the receiver only may be connected while under outgoii'ur transmission, the transmitter only may he connctaed to the exterior or service leads of a set. Therefore, under transmission in either direction from a set, all of the speech currents may he availahlc as useful energy for traversing a line and finally actuat in; the reeeiver at a distant station.

In situations where it may he dcsircd to provide hcnclicial side-tone. as above dcscrihed. the switching system has been arranged in such a manner that a limited amount only of the speech energy from a transmitter may he directed into the associat ed receiver. the path of such energy being adapted substantially to exclude current ctfects which would ot'lu. rwis set up dctrimental side-tone cticcts.

The coordination of the circuits of a telephone set of the present system automatically to render hut one oi the lItlllSllliI-fl-lflll devices, as the t ransinittcr or the INtlYnl respe tively. effective at one time with the leads serving :1v set, results in 'nullitiyinp energy heretofore ell'ective in setting up dct rimcntal sidetrone or echo cil'ects peculiar to fil-dl'il line circuit arrangements.

In n'oviding a telephone set. to comhinc the several advantages oi elimination of wasteful loss of speech. elimination of detrimental side-tone effects, nullifyinn' of e ho effects with provision for applying busy tcst operations. the devices of the present invention have been coordinated in such a man" Hill .naangaei 1 shows a. telephoneset iprovi died with i a relay system "controllable :by energy from voice currents for automatically switching the circuits of the set to prevent wasteful Lloss of speech energy, for eliminating detrimental side tone while affording beneficial side tone effects and for rendering echo efi'ects ineffective.

Fig. Qshows a telephone set which differs 3 from the sct-ofFig. 1 principally :in thataill side-tone effects are eliminated, While details o-f-the relay system also dii'ier from the i system of the iirst figure.

Fig. 3 showsa setarrangement which dif fers from that of' F-ig. 1 principally in that the relay systeinhas been simplified.

ig. 4 shows a setwhich difiers from that of Fig. 1 principally in that a vacuum tube is-employed in the relay system, while in Fig. -5 a set is shown which in addition to providingthe service features of thesetshown in Fig. -1" also provides tfor the-carrying out of busy test indications.

Other objects and features of the present invention will be apparentfifrom the followilrgdescri otion and the appended claims:

Th'roug out the various 'views of the drawi'ng like charactersdf re'i erenoe haveheen employed for indicating likeor similar parts.

in a more detailed description of this systeillyCODClflCtOIS 1' and 2 serive a receiver -3 and transmitter a of a telephone set -'(F=ig. 1) In the normal position of the circuits which is the position shown in the drawing, it may he noted that the lowercontacts of a: norn'iail iy energized relay 5 serve to establish the receiverS rli-rectlyto the conductors 1 'andiZi A retardation corl '6 1S shunted during such periods due to this closed CODClil/IOD of the contacts of therelay 5, while the secondary winding of an induction coil 7 is retained open at the upper contacts of' 'this relay 5.

Therefore, voice V-eurrents which may arrive over the leads 1 andQ may complete circuit through the receiver 3 o'nly, as all other paths "from these conductors*a-redisconnected.

For outward transmission, current "from a battery '10 may energize a-loca l circuit formed of a retardation coil 11, the transinittcr 4 and the primary windingertile induction coil 7 Thereactance 01* the coil 11 substantially prevents changes of current effectto thehattery' as may be set up by Voice eifectsin the transmitter 4; Therefore, a condenser 12 is connected in bridge on the series forn edofthe transmitter iand the primary winding oi" the induction coil 7 'icit the purpose of permittin g the necessary Voice frequency changes to he established in the induction coil. Connected in parallel with the-condenser '12 is ,a series formed of a condenser 13 and a SGIlSllZLVB alternating curol the acceleration type shown in 'my copending applicationfserial No. 526,152, iiled Dec. 31, 1921. Normally the contacts of the relay l lr'are closed .in completing an obvious circuit from grounded battery to retain the relay-h energized. transmitter i may be in. use, however, the

hi 'hspeed relay ll responds to the alternat ling. currents,corresponding with changes in potential level-on the condenser 12, and n1a1ntains its contacts separatedin disconnecting the relay 5. Therefore, so long asvoicee f- WVhen the g aren't relay-14. This relay may preierablyhe iects may be present from" the transmitter V iythe relay'5 will stand released. thereby removing the shunt fron around the impedance coil 6 in. series-With the receiver 3 as connected tothe leads 1 and 2, while 010- sureol' the upper contacts of the relay 5 will connect the secondary winding of the induction coil 7 to the conductors 1 and 2. In

the latter position o'fthe circuits, the'trans mitter i is rendered effective for transmission over the pair formed of conductors 1 i and 2, While a series path formed ofthe re ceiver 3 and the impedance 6 is connected in bridge on this pair. Due tothe presence "become directive in the-receiver?) and serve as beneficial sidestone, 'The presence of the retardationcoil in series with the 'receiyer results in a minimum amount oi energy in this patl Therefore, a maX-imumnmount of the venergy;wliich may he set up through the transmitter l may he eil'ective i'or transmission oyer the conductors 1 and 2 to the receiyer at a distant station, (not shown Suitable proportioning of the capacity 13 in relation to the inductance :ofthe relay 14 should he providedwto prerenta condition of series resonance for, the relay 1e either through thecondenser 12-01 through the primary Winding of the induction coil 7 and the trans1nitte1'- l,at frequencies other than voice range. p

lin addition to supplying heneficial'sidetone from :the transmitter ,4, the presence of the receiver 3 on the exterior conductors 1 and 2 chiming outward transmission from the telephone set under description,also, serves for reception'of any indication from adistant station at which the other party to a conversation .may speak "in seeking to interrupt aspeaker when suchlaction, maybe dethe outputcircuit; of: the transmitter and connect the receiver alone for reception of all energy which may arrive from over the conductors l and 2.

In the arrangement of Fig. a resistance is interposed in the current supply path for the relay 5, while the contacts oi the relay it are connected to normally shunt down the relay 'lhcretorc, the latter rclay is normally (lo-energized and in order to correct or such inverse position of this relay with regard to the corresponding rcay of Fig. l the leads to the contacts ot' this relay have been tramposcd. Uinission of the rcactcnce it in the arrangement ot Fig. 2 to dispense with all side tone ctleets. in the normal position ot' the circuits the relay 5 will stand in the position in which it is shown in the drawing. thereby establishing the receiver :3 to receive all energy which may arrive from over the leads 1 and 53.

In this arrangement the circuit. of the relay l-t is connected in parallel to the sccondary winding of the induction coil 7. Therefore. under speech cnero'y at, the arsociated transmitter =1 relays i and a will respond to cti'ect entire ('ll-StOllilQ'ilOtl ot the receiver 23 and connection at the output circuit ot' the transmitter system to the conductors l. and L. ',l.heretorc. all of the speech energy created in the transmitter ma become etl'ective over any 'torm of line circuit which may be connected to the leads 1 and 2.

In the arrangement of Fig. :3 the secondary winding of the induction coil is permanent y connected to the conductors l and 2. while the receiver 3 is also connected to the latter conductors in such a manner that a resistance or impedance 6 is normally shunted by the closed contacts oi the relay l-l. heretorc, 'tor incoming currents from over the conduchas 1 and 2 the receiver 3 will be connected in parallel with the output circuit of the iuduction coil 7. in this arrangement the circuit ol. the relay 1-1 is connected in bride'e around the transmitter t. Under operation of the transmitter the response of the relay llremoves the secondary windiug of induction coil 7 and interposcs the resistance 6 in series with the receiver 3. This placed the receiver in condition to atlord beneficial side tone as already described for the telephone set, ot Fig. 1. Under reception of incoming transmission, the secondary winding of the induction coil may absorb some of the a rri vin energy. 'lheret'ore, the use of this arrangement may bolimited to situations where this loss of energy may not seriously atiect the transmission.

In the arrangement; of F d a three element vacuum tube amplifier rectifier 18 has been substituted for the acceleration or vibratory type relay let of the other arrange ments. In the drawing, the elements of the tube have been shown in conventional form. A grounded A battery A supplies current;

for the filament or cathode element. The grounded. source 10 serves in supplying: C battery potential by way of the retardation coil 11 and a resistance 19 to the grid or control element, while a grounded 1% battery B supplies current by way ot' the winding of the relay .1 to the plate or anode element of the tube. Normally the negative potential of the t battery establishes a condition of bias in the tube to limit the current. through the relay :3 so that this relay may be inert. as shown in the drawing. l ndc'r this condition, the resistance (5 will he shunted, and the receiver 23 will be conziei-twl to the service leads l and 2. while the output circuit of the induction coil will be disconncctcd. Under voice eti'i-cts from the transmitter -t. the re- Still'lt1f f])()ittltlttl changes at the condenser 12 will overcome the negative bias oi the tube 18 to permit sutiicicnt current in the plate circuit; to eli'ect: response of the relay This switches the lOHtlS i and. :2 to the out mt circuit ot' the transmitter ti while the resistance (3 will be established in series with the rcceivcr 3 which will thus be a bridge across the coinluctors 1. and The service etl'ects with this arrangement sul'istautially correspond with those already described for the arnmgemcntol Fig. 1.

in the arrangement; of Fig. 5 the leads 1 and 2 may be considered as extending to an order wire or ca ll circuit; terminating at a distaut exchange point: while the leads 2]. and 22 may be considered as joined to line conductors which form a trunk circuit terminating at the same distance exchange (not shown). A plug, 23 serves for terminating this trunk or toll line circuit at an exchange in association with the systen'i of Fig. This trunl; circuit may be considered as one of a group of trunk circuits which may terminate at; a switchboard position served by the telephone set now under description.

Let it now be assumed that; a distant operator transmits a request by way of the call circuit, conductors 1 and 2, for a certain connection. The receiver 3 stands normally connected by way ot the upper contacts of the relay 5 to these conductors for reception of such requests. Assuming now that the operator assigns the trunk circuit ending in plug '23 or such a connection, this iut'ornia- 'tion will be given to the distant originating operator over the same call circuit. For this, speech at the trimsmitter l etl'ects response ot the relay l-t. the circuit. ol which is in parallel with the primary winding; ot the induction coil T in this arrangement. This removes the shunt to permit response of the relay 5, thereby switching the leads 1 and 2 to the output winding the induction coil 7, and also inserts the left hand winding of a transformer 25 in series with the receiver 3 as now joined to the conductors l and 2. This winding of the transformer now ti-l Ito

lid

serves as an impedance similar to the unit 6 of the other arrangements, for restricting the amount of the outgoing energy which may become effective through the receiver as desirable or beneficialside-tone. V

In proceeding to establishthe desiredconnection the inward or switching operator first tguches the tip (uppermost) member of the P shown) of the desired line, thus making a busy test operation to determine whether the line is idle. Assuming now that the line may be busy, potential from. grounded battery Will be present on the shell of the assumed jack and current may flow over the uppermost member of the plug 23, the normal or upper contacts of a relay 26, thence to ground through the right-hand or primary winding of the: busy test transformer or repeating coil 25. This establishes an impulse of induced current in the left-hand or output winding of the repeating coil. his impulse may traverse a closed loop which includes the telephone receiver 3 and the secondary winding of the induction coil 7.] The resulting click in the telephone receiver indicates that the desired line is busy. Due to the character of the sound produced by such busy test operations they are commonly referred to as click busy tests. 1

In the event that the desired line may have been idle, absence of battery potential at the assumed jack would have resulted in no sound when the test was made. Therefore, in establishing the connection, the plug 23 may be assumed to have been inserted into the jack (not shown). Current from grounded battery through the winding of a rela 26 would then flow over the lowermost or sleeve strand of the connection, the jack portion of which is well understood in the art and therefore has not been shown in the drawing. Response of the relay 26 switches the upper strand of the cord circuit from the busy test coil 25 to the conductor 21 of the trunk circuit. In this manner, the circuit of the trunk is isolated from the telephone set and thecircuitis completed for use on the connection established.

It will now be clear that the transformer 25 has a dual use, as it serves atone time as a busy test coil and at anothertime as a retardation coil, relativeto preventing detrimental side-tone while permitting beneficial side-tone to become effective through the receiver 3.

The telephone set of Fig. 3 may also be employed at switchboard positions where ordinary cor'd circuits may be present. For this, a second plug in duplicate of the plug 23 may be joined to the conductors 21 and 22. These conductors will then form the 23 to the shell member of a jack (not two main strands of the cord circuit. A socalled talkmg key (not shown) may then be considered as present for joining the busconductors 1 and 2 of the operators set to the conductors 21 and 22 of the cord circuit.

From the description already given it will be obvious how such a key may render the telephone set effective for performing busy m1: y then correspond with the arrangement of Fig. 2 relative to entire elimination of the telephone receiver 3 during periods the associated transmitter l of a set may be in use.

The relay to respond quickly in connecting the circuits of the associated transmitter but somewhat slow to respond in the direction of CllSCOIl".

necting the output circuit of the transmitter from the exterior leads. This is moreparticularly to prevent switching eifects between syllables or words' The delay or lag effect, however, to be such that switclt ing may take place immediately following definite cessation of speech at an associated transmitter. The delay characteristics have been indicated by conventional markings in the drawing.

lvhat is claimed is:

1. In a telephone set circuit, a transmitter system including a transmitter, a source of current and an induction coil having a primary and a secondary circuit, a receiver, a service lead connected to said receiver, and switchingmeans responsive to voice currents in the primary circuit of said induction coil for transferring said lead from the receiver to the secondary circuit of said induction coil.

' 2. In a telephone set including a transmitter, a source of current,a receiver, an induction coil, a retardation coil and a transmitter, a primary circuit including 5 preferably should be of a type j said source, retardation coil, transmitter and one winding of said induction coil, a condenser connected in bridge of the series formed of said transmitter and said winding of the induction coil, a service lead normally connected to said receiver, and relay means connected in parallel with said condenser and responsive to current impulses generated by said transmitter for transferring said lead from said receiver to the other winding of said induction coil.

In witness whereof, I hereunto subscribe my name this 30th day of March A. D., 1926.

- HENRY W. ONEILL. 

